This was the 1970s. Autism — a spectrum of disorders with a range of effects on brain development — was poorly understood and rarely diagnosed.

Many child development specialists still blamed what had been labeled "refrigerator mothers" or "refrigerator parents" for failing to nurture the emotional and verbal skills missing in many autistic children.

Awareness of the disorder's true genetic and neurological causes was only beginning to emerge.

So Tom Hogan was peering into a barren world on the day, when Danny was 2, that Tom realized something was wrong.

He was babysitting a child near the same age as Danny, and he saw a vast difference in their abilities to communicate and interact.

He didn't understand it and he didn't know where he could turn for help.

They walked alone out in the woods a couple of days later, Tom Hogan said. And he determined then that he would accept whatever life was preparing to deal them.

"I told him, 'I'm always going to be there for you.' "

Less than two weeks before Danny Hogan's 40th birthday, Tom Hogan took him to the Special Olympics Christmas dance at the Roeland Park, Kan., Community Center.

When one of the program coaches swung him out onto the dance floor, Danny went with her, circling hand in hand. But left to his own, he preferred to wander the perimeter, examining the grills on air ducts or the lights on the tabletop Christmas tree.

"I used to wonder, 'Is he missing things?' " Tom Hogan said.

Tom Hogan and Danny's mother, Jacqueline Hogan, divorced when their son was a toddler. They shared custody through most of his boyhood years, and Tom became Danny's sole guardian beginning in his high school years.

Tom and his second wife, Jennifer, had a daughter, Lindsey, when Danny was 14.

Through the years, Danny saw Lindsey grow up, play with friends, get a driver's license, have boyfriends, go to college, get married.

Page 2 of 3 - But if he envied her or felt cheated, he never showed it, Tom said.

Danny works at Johnson County Developmental Supports in Kansas, where he earns a small paycheck doing tasks for area businesses.

He enjoys the family's weekly night out to dinner. And he and Tom for years have been going to most every Kansas State University home football game.

Just what Danny Hogan thinks about his milestone birthday is mostly a mystery.

He acknowledges it with the sparest of words and expressions, leaving his thoughts up for interpretation, like the artwork he has created over the years.

One painting is framed on the wall by the Hogans' kitchen table. Its dense swirl of thick-stroked lines casts pearls of purple, blue and red in a blue-green sea.

"He seems content," Tom said. "He's comfortable with his life."

Tom has watched the world's awareness and understanding of autism grow over the four decades.

In the 1970s and into the 1980s, roughly one in 2,000 children was diagnosed with autism.

It was during that time, Tom Hogan recalled, that he took Danny horseback riding, and when he told a woman helping them that Danny was autistic, she replied, "So he draws really well?"

The number began to grow, and it exploded in the 1990s and 2000s, to the point that the Centers for Disease Control and Prevention now estimates that one in 88 children is diagnosed with autism — and one in 54 boys.

The rapid growth alarmed the research community, which is still struggling to determine how much of it is the result of greater awareness and how much is the result of underlying causes.

Tom Hogan and Danny's sister, Lindsey Minnick, have had a close view of society's evolving understanding of autism.

Counselors and therapists are growing more precise in attending to the needs of each autistic child and adult. They are making more efforts to mix children with disabilities into general education classrooms and activities.

As a parent and as a board member on many of the service organizations that have helped Danny, Tom has watched times change.

Lindsey took her experience growing up with Danny and turned it into a career as an instructor at Firefly Autism, a school in Denver.

"He made my life what it is," she said.

In her high school years at Shawnee Mission North in Overland Park, Kan., Lindsey said, she avoided a lot of the typical adolescent angst because she could see how Danny had few worries and enjoyed the simple things that he held or watched.

Instead of worrying much about popularity or how she looked, Lindsey said, she volunteered to help special education students.

Page 3 of 3 - For Tom Hogan, it has been a fulfilling 40 years.

"People talk to me sometimes like it's been this burden," Tom said. "But it's not like that at all. He's my companion. He's my friend."

Meanwhile, Danny Hogan keeps developing communication skills, working regularly with a therapist to recognize and acknowledge other people's emotions and expressions — and share his own.

"Here's my proud face," the therapist, Jaresa Ross-Bey, said in the Hogans' living room. She held her head high, beaming a smile, her hands on her hips. "Let's see yours!"